Spatio-temporal study and population structure of Daptonema oxycerca (Nematoda: Xyalidae) in Coroa Grande, Rio de Janeiro, Brazil

Abstract

Daptonema oxycerca was originally described from the North Sea and, up to now, nothing is known of this species in tropical regions. The spatio-temporal distribution and the population structure of this species was studied during one-year period (from May 1998 through April 1999) in Coroa Grande, Rio de Janeiro, Brazil. For sampling, two fixed, parallel transects were established perpendicularly to the shoreline, and at each transect, four, equally spaced levels were marked to represent the upper and the low intertidal zones. The lowest temperatures occurred in the end of the austral winter and first month of the spring and the highest temperatures occurred in the austral summer. The density of D. oxycerca varied during the year, with a peak in August. This tendency was observed for mates, ovigerous females, and non-ovigerous females. The species density was negative correlated with temperature. The sex ratio was not statistically significant. D. oxycerea was most abundant at the upper intertidal level in both transects. This work provides the first record of D. oxycerca in Brazil, and confirms the influence of temperature in regulating its population density.